In one type of high voltage transmission system, the high voltage transmission lines are supported from metal towers by insulator assemblies that may be ten or more feet in length. Each insulator assembly comprises a string of insulators fastened together end to end, with each insulator including a pin, a cap, and an intervening hemispherical shell of insulating material such as glass. Pins and caps of adjacent insulators are connected together in a ball and socket fashion, and the connections are secured by cotter keys to produce the complete insulator assembly.
During maintenance of high voltage transmission systems, it frequently becomes necessary to remove or replace insulator assemblies while the high voltage line to which the assembly is connected is "hot." Removing or replacing an insulator assembly involves partially removing or inserting one or more of the cotter keys that secure the individual insulators to one another or to the transmission line or tower. Because the line is hot, the cotter keys must be manipulated by a tool held on the end of a long (e.g., 15 foot) insulating handle. One known tool consists of a small hook for engaging the rounded head of a cotter key, so that the cotter key can be hooked and partially removed by pulling on the insulating handle. However, engaging the head of a cotter key with a small hook at the end of a long handle can be a difficult process, particularly in a high wind. In addition, it is necessary to recess the heads of the cotter keys into the insulator caps to avoid undesirable high voltage corona discharges, a feature that greatly increases the difficulty of engaging the cotter key head with a hook. Using hook shaped tools, it is not uncommon for maintenance personnel to spend an hour or more removing a single cotter key from an insulator assembly.